Headlights won't burn on 1986 911 Porsche. I've checked the fuses and the bulbs. Tail lights and park lights burn but headlights don't.

Hi Julie let's see what we can do here go back to the rear socket you have front parking lights yes/no if yes the the problem is either corrosion inside the socket or a wire is broken or the headlight or brake light switch so first let's do this turn on headlights see if all lights are on (parking tail headlights next change to just parking lights check again next use 4 way flashers and next use brake pedal there are 2 filaments in each bulb and you need to record when it's not working so EX.HEADLIGHTS PARKING LIGHTS ARE IN 1 FILAMENT ////BRAKE LIGHTS TURN SIGNALS AND 4 WAYS THE OTHER ONE IF AFTER CHECKING THERE IS STILL NOTHING ON THE LEFT SIDE AT ALL NOW IT'S A WIRE OR THE SOCKET IF THERE'S ALSO NO PARKING LIGHT IN THE FRONT IT'S THE SWITCH FOR THE HEADLIGHTS GET A GUY TO CHECK THE WIRE CONTINUITY OF THE TAIL LIGHT FROM THE HEADLIGHT SWITCH AND THE POWER COMING OUT FOR THE LEFT SIDE TAILIGHT AND CHECK THE BULB SOCKET FOR THE SAME CONTINUITY TO GROUND AND FOR 12 VOLTS YOU DIDN'T LIST WHAT VEHICLE THIS IS BUT THE PROCESS IS THE SAME A CORRODED LIGHT SOCKET MAY BE YOUR PROBLEM HERE WHEN YOU CHANGED THE BULB WAS IT BLACK AND CLOUDY LOOKING OR JUST CLOUDY WHITISH LOOKING WATER COULD BE GETTING INTO THE TAILIGHT CAUSING A SHORTING CONDITION AND COULD HAVE BURNED OUT THE SOCKET

Are the front park lights operational? These are tied into the tail lights as well. If the front park lights are operational and the rear are not, suspect bad/burned out bulbs. If no park lights operational, suspect fuse or wiring

they are dual filament bulbs so the tail light filament might have blown and not the stop light , replace the bulb to check

These are all different circuits. The brake lights are on a 10amp fuse - the headlights are on a 50amp fuse - and the parking and dash lights are on a 20amp fuse.
Do you have power going into the headlight switch and the brake light switch ?

First you have to make sure the bulbs are good, if they are check out good, you need to check the fuses and switch.
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New Slim hid ballast

it does happen that the bulbs burn out and you never noticed the first one burn out so check for power to the bulbs and then check the fuses the head lights are on a different fuse then the parking lights

First check tail light fuse and the parking light relay

most likely the fuse, have you checked that? Do the other outside lights (other than headlights) work? (side markers, parking lights) If they are also out, it's almost certainly the fuse.
If that's ok, check the bulbs themselves. Sometimes they burn out one at a time, if you don't pay attention, they can all burn out before you notice.

The relay has nothing to do with the tail lights, but replacing the switch sounds like a good idea. There's a nut holding it in place, see http://www.skandix.de/en/spare-parts/electrics/switches/switch-headlight/1027524/ to get an idea of the construction. And the price. This is not worth fiddling about unreliable workarounds...
In addition, if fuses 15 and/or 16 burn frequently there might be a problem with the tail light cabling.

Good luck
Ingo

ok supaxang, could this solution be as simple as replace the 2 rear bulbs? The brake light and tail light (parking light) are the same bulb, 2 filaments, one for brakes, one for tail lights. If the the tail light filament burns out, the brake light will continue to work ok. It is quite possible that both tail lights burned out, and the brake light filaments are good and still working. Replace w/ bulb #2057. Let me know if this fixes it, if not, I'll keep working on it.